1. Field of the Invention
The present invention relates to an apparatus and method for measuring ground amounts of a display panel, and more particularly, to an apparatus and method for measuring ground amounts of a liquid crystal display panel.
2. Disclosure of the Related Art
In general, a plurality of thin film transistor array substrates are formed on a first large-sized glass substrate and a plurality of color filter substrates are formed on a second large-sized glass substrate in order to improve fabrication yield of liquid crystal display devices. Then, the first and second substrates are attached together to simultaneously form a plurality of unit liquid crystal display panels. Accordingly, a process for cutting the liquid crystal display panel into a plurality of unit liquid crystal display panels is required.
The cutting of the unit crystal display panels is commonly performed such that a scribing line is formed on a surface of one of the first and second substrates using a wheel have a hardness greater than a hardness of the first and second glass substrates in order to propagate a crack along the scribing line.
FIG. 1 is a cross sectional view of a plurality of unit liquid crystal display panels according to the related art. In FIG. 1, a plurality of thin film transistor array substrates 1 protrude along sides of a plurality of color filter substrates 2. In addition, a gate pad unit (not shown) and a data pad unit (not shown) are formed along marginal portions of the thin film transistor array substrates 1 that do not overlap with the color filter substrates 2. Accordingly, the color filter substrates 2 are formed on a second substrate 30 and are isolated by dummy regions 31 corresponding to protruding portions of the thin film transistor array substrates 1 that are formed on a first substrate 20.
The unit liquid crystal display panels are suitably disposed such that an area of the first and the second substrates 20 and 30 may be efficiently utilized. In addition, the unit liquid crystal display panels are usually isolated by the regions 32.
After the first substrate 20, which includes the thin film transistor array substrates 1, and the second substrate 30, which includes the color filter substrates 2, are attached to each other, the liquid crystal display panels are cut into individual unit liquid crystal display panels. Accordingly, the dummy regions 31 and regions 32 are removed during cutting.
FIG. 2 is a plan view of a unit liquid crystal display panel according to the related art. In FIG. 2, a unit liquid crystal display panel 10 includes an image display unit 13 in which liquid crystal cells are arranged in a matrix form, a gate pad part 14 connecting gate lines (GL1 to GLm) of the image display unit 13 to a gate driver integrated circuit (not shown) to which a gate signal is supplied, and a data pad part 15 connecting data lines (DL1 to DLn) of the image display unit 13 to a data driver integrated circuit (not shown) to which image information is supplied. The gate pad part 14 and the data pad part 15 are formed along marginal portions of the thin film transistor array substrate 1 and protrude from a short side and a long side of the thin film transistor array substrate 1, as compared to the color filter substrate 2.
Although not shown, a thin film transistor switching the liquid crystal cells is formed at each of intersectional portions of the data lines DL1 to DLN and the gate lines GL1 to GLm of the thin film transistor array substrate 1. Furthermore, a pixel electrode is connected to the thin film transistor for supplying an electric field to the liquid crystal cells, and a passivation film is provided for protecting the data lines DL1 to DLn and the gate lines GL1 to GLm, wherein the thin film transistors and a pixel electrode are formed on the thin film transistor array substrate 1. In addition, color filters are separately coated at the cell regions by the black matrix and a common transparent electrode, which is a counter electrode of the pixel electrode formed on the thin film transistor array substrate 1, are provided on the color filter substrate 2.
A cell gap is formed between the thin film transistor array substrate 1 and the color filter substrate 2 so that they are separated with a gap formed there between. The thin film transistor array substrate 1 and the color filter substrate 2 are attached by a sealant (not shown) formed along an exterior of the image display unit 13, and a liquid crystal layer (not shown) is formed within the gap between the thin film transistor array substrate 1 and the color filter substrate 2.
Although not shown, a shorting bar is formed at the marginal portion of the thin film transistor array substrate 1 to prevent electrostatic discharge that may occur when conductive films are patterned on the thin film transistor array substrate 1. The shorting bar is removed after the liquid crystal display panels are cut to individual unit liquid crystal display panels. Thus, marginal portions of the unit liquid crystal display panel are ground to remove the shorting bar. In addition, grinding of the marginal portions of the unit liquid crystal display panel adversely causes generation of fragments within the marginal portion of the unit liquid crystal display panel due to exterior impact. Accordingly, an operator may be injured by the sharp fragments of the marginal portions of the unit liquid crystal display panel.
FIG. 3 is a schematic view of a grinding device for a liquid crystal display panel according to the related art. In FIG. 3, a grinding device includes a loading unit 50 that loads a cut unit liquid crystal display panel 10, a grinding unit 53 that receives the unit liquid crystal display panel 10 loaded at the loading unit 50, aligns the unit liquid crystal display panel 10 at a grinding table 51, and grinds a marginal portion of the unit liquid crystal display panel 10 using a grinding wheel 52 rotated at a high speed, and an unloading unit 54 that receives and unloads the ground unit liquid crystal display panel 10 from the grinding unit 53.
FIG. 4 is a perspective view of an apparatus for measuring a grinding amount of a liquid crystal display panel according to the related art. In FIG. 4, the marginal portions of the unit liquid crystal display panel 10 are ground to have sloped edge portions along upper and lower surfaces. In general, the upper marginal portion of the unit liquid crystal display panel 10 where the shorting bar is formed is ground more than the lower marginal portion of the unit liquid crystal display panel 10.
In order to measure the ground amounts of the unit liquid crystal display panel 10, a camera 60 is installed at an upper side of the marginal portion of the unit liquid crystal display panel 10 to create and image of the upper marginal portion of the unit liquid crystal display panel 10. As the operator inspects the image of the upper marginal portion of the unit liquid crystal display panel 10, the operator may determine whether the ground amount is adequate.
FIG. 5 is a plan view of a photographic image produced by a camera according to the related art. In FIG. 5, an image C1 photographed by the camera 60 (in FIG. 4) shows a grind width W1 of the upper marginal portion of the unit liquid crystal display panel 10. However, the apparatus for measuring the ground amount of liquid crystal display panel has the following problems. First, since the camera 60 (in FIG. 4) is installed at the upper side of the marginal portion of the unit liquid crystal display panel 10, photographic images of only the upper marginal portion of the unit liquid crystal display panel 10 are obtained. Accordingly, photographic images of the lower marginal portion of the unit liquid crystal display panel 10 are not obtained, thereby making it impossible to determine whether the lower marginal portion of the unit liquid crystal display panel 10 has been adequately ground. Thus, the lower marginal portion of the unit liquid crystal display panel 10 may be defective, which would result in a defective liquid crystal display panel and a yield degradation.